<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>js变量</title>
		<script>
			/*var i = 3;
			alert(i);
			
			i = "abc";
			alert(i);*/
			//定义number类型
			var num = 1;
			var num2 = 1.2;
			var num3 = NaN;
			//输出到页面上
			document.write(num + "<br />");
			document.write(num2 + "<br />");
			document.write(num3 + "<br />");
			
			//定义string类型
			var str = "abc";
			var str1 = 'efg';
			document.write(str + "<br />");
			document.write(str1 + "<br />");
			
			//定义Boolean类型
			var flag = true;
			document.write(flag + "<br />");
			
			//定义null undefined
			var obj = null;
			var obj1 = undefined;
			var obj2;
			document.write(obj + "<br />");
			document.write(obj1 + "<br />");
			document.write(obj2);
		</script>
	</head>
	<body>
	</body>
</html>
